For centuries the shape-shifting mermen of the Morvann Islands have lived incognito among humans. But one of them, Yann, has developed some bad habits. Like rescuing humans, even when doing so risks revealing his true nature. When he fishes Alex out of the sea, he doesn’t expect her to reappear eight months later, and turn his life upside down by asking him to be her guide. Alex is determined to fulfil a promise to her dying grandmother, by gathering pictures and stories of the Morvanns. But she soon discovers that, on these remote Welsh islands, legends have a habit of becoming true! Over the course of a few days, Yann and Alex grow close. But some mermen hate humans. Their hostility, and Yann’s secret, threaten to tear the couple apart just as they are discovering that they are soul mates. Can Yann overcome the obstacles in his path and make the right choice?